The invention relates generally to inkjet printers, and in particular to a method of cleaning a printhead in an inkjet printer.
Typically in continuous inkjet printers, a pressurized ink is formed into continuous inkjet filaments which project from closely spaced ink discharge nozzles in a nozzle plate on a printhead. Filament stimulation sources such as ink heaters or transducers operate as ink droplet generators each time they are activated, by causing filament end-lengths to be broken off at the respective nozzles. The broken-off filament end-lengths form discrete ink droplets which are deposited on a print medium moving relative to the printhead. The interval between successive droplet break-offs at any one nozzle matches the interval between successive activation""s of the filament stimulation source for that nozzle. The longer the interval between successive activation""s of the filament stimulation source for the nozzle, the longer the opportunity for the continuous inkjet filament to increase lengthwise at the nozzle and the larger the ink droplet. Conversely, the shorter the interval between successive activation""s of the filament stimulation source for the nozzle, the shorter the opportunity for the continuous inkjet filament to increase lengthwise at the nozzle and the smaller the ink droplet. Thus, the volume of the ink droplet, when a droplet break-off occurs at the nozzle, corresponds to the frequency of activation of the filament stimulation source for the nozzle.
Successive ink droplets resulting from droplet break-off at the nozzles often are altered between printing and non-printing trajectories or paths. Those ink droplets that are in a printing trajectory are allowed to reach the print medium. Those ink droplets that are in a non-printing trajectory can be collected in a ink gutter or catcher and then recycled back to an ink reservoir that empties into the nozzles in the printhead.
A known problem is that organic debris deposits such as dirt, dried ink, and/or microorganisms can accumulate within the nozzles and/or within the ink reservoir for the nozzles. Moreover, the debris deposits can accumulate on the nozzle plate, particularly in the regions that droplet break-off occurs at the nozzles. The debris deposits must be removed. Any debris deposits on the nozzle plate, in the regions that droplet break-off occurs at the nozzles, can cause the ink droplets to be misdirected from the printing trajectory that they should take to reach the print medium. Consequently, the printed image may be of a lesser quality. Any debris deposits within the nozzles can render the nozzles defective by clogging them.
Cleaning to remove the debris deposits from the printhead can be done by flushing a cleaning solvent under positive pressure into the ink reservoir and outwardly through the nozzles, and by flushing the cleaning solvent over the nozzle plate.
A method of cleaning a printhead in an inkjet printer by removing organic debris deposits from the printhead, said method comprising:
applying anyone of the liquid mixes of NaOCl (sodium hypochlorite) and H2O (water), H2O2 (hydrogen peroxide) and H2O, Na2S2O4 (sodium hydrosulfite) and H2O, CaCl2O2 (calcium hypochlorite) and H2O, or KMnO4 (potassium pernanganate) and H2O on the debris deposits, to serve as a cleaning agent;
drying the cleaning agent applied on the debris deposits, to leave a residue with the debris deposits; and
washing the residue with the debris deposits off the printhead. Preferably, the cleaning agent applied on the debris deposits crystallizes on the debris deposits during drying in order to leave the residue with the debris deposits and to shrink the debris deposits.